REVIEW CURRENT OPINION Hypotension after spinal anesthesia for cesarean section: how to approach the iatrogenic sympathectomy Christina Massotha, Lisa To¨pelb, and Manuel Wenkb Purpose of review Hypotension during cesarean section remains a frequent complication of spinal anesthesia and is associated with adverse maternal and fetal events. Recent findings Despite ongoing research, no single measure for sufficient treatment of spinal-induced hypotension was 05/25/2020 on BhDMf5ePHKbH4TTImqenVDezntqwKeJGjCYTUOBBz0EyVSh+WquM7uJo3U//pWTO by http://journals.lww.com/co-anesthesiology from Downloaded Downloaded identified so far. Current literature discusses the efficacy of low-dose spinal anesthesia, timing and solutions for adequate fluid therapy and various vasopressor regimens. Present guidelines favor the use of from phenylephrine over ephedrine because of decreased umbilical cord pH values, while norepinephrine is http://journals.lww.com/co-anesthesiology discussed as a probable superior alternative with regard to maternal bradycardia, although supporting data is limited. Alternative pharmacological approaches, such as 5HT3-receptor antagonists and physical methods may be taken into consideration to further improve hemodynamic stability. Summary Current evidence favors a combined approach of low-dose spinal anesthesia, adequate fluid therapy and vasopressor support to address maternal spinal-induced hypotension. As none of the available vasopressors by is associated with relevantly impaired maternal and fetal outcomes, none of them should be abandoned BhDMf5ePHKbH4TTImqenVDezntqwKeJGjCYTUOBBz0EyVSh+WquM7uJo3U//pWTO from obstetric practice. Rapid crystalloid co-loading is of equivalent efficacy as compared with colloids and should be preferred because of a more favorable risk profile. Keywords cesarean section, fluid therapy, hypotension, spinal anesthesia, vasopressors INTRODUCTION Interestingly, increased susceptibility for hypo- Spinal anesthesia is the most frequently used tech- tensive events following neuraxial sympathetic block nique for elective cesarean section in the developed occurs as a result of gestation-induced cardiovascular world, provided for about 78% of procedures [1]. and mechanic alterations in hemodynamics. Minimizing side effects of neuraxial block may During late pregnancy, compression of the infe- somewhat be challenging as cephalad block distri- rior vena cava by the gravid uterus in supine posi- on tion could cause a sudden decrease in preload and 05/25/2020 butions up to Th4 are required for operative delivery and parturients show an increased susceptibility to subsequent fall in cardiac output. However, MRI the effects of local anesthetics. It is well known that iatrogenic sympathetic block causes arterial and venous vasodilation and leads to a decreased systemic vascular resistance aDepartment of Anesthesiology, Intensive Care and Pain Medicine, b with a reduction of preload and afterload. High University Hospital Munster,€ Munster€ and Department of Anesthesiol- levels of spinal distribution may cause bradycardia ogy, Intensive Care and Pain Medicine, Florence – Nightingale – Hospital Dusseldorf,€ Dusseldorf,€ Germany and decrease of stroke volume by blocking acceler- Correspondence to Manuel Wenk, MD, Department of Anesthesiology, ating sympathetic cardiac fibers. Decreased right Intensive Care and Pain Medicine, Florence – Nightingale – Hospital, ventricular filling may also trigger mechanorecep- Kreuzbergstraße 79, 40489 Dusseldorf,€ Germany. tors in the cardiac wall, resulting in vasovagal Tel: +49 211 4092300; fax: +49 211 4092037; Bezold–Jarisch reflex, associated with sudden pro- e-mail: [email protected] found bradycardia, vasodilation, and a potential Curr Opin Anesthesiol 2020, 33:291–298 cardiovascular collapse. DOI:10.1097/ACO.0000000000000848 0952-7907 Copyright ß 2020 Wolters Kluwer Health, Inc. All rights reserved. www.co-anesthesiology.com Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. Obstetric and gynecological anesthesia lower during normal pregnancies in comparison to KEY POINTS the nonpregnant state [4,5]. This emphasizes that Spinal-induced hypotension is a frequent complication maintenance of maternal hemodynamics in the during cesarean section and can most effectively be status quo is already relying on incomplete compen- addressed by a multimodal approach. sation. A further reduction in peripheral vascular resistance, as through spinal anesthesia-induced Amongst various regimens and methods, current iatrogenic sympathectomy, could easily exceed evidence favors the combination of low-dose spinal anesthesia, high-flow crystalloid co-loading, and compensatory capacities, eventually causing a sig- vasopressor administration. nificant hemodynamic impairment. It, therefore, comes as no surprise, that arterial As neither ephedrine nor noradrenaline or hypotension is one of the most frequent complica- phenylephrine are associated with worse fetal tions of spinal anesthesia for cesarean section and outcomes, application of any substance may be considered on a case-by-case decision. appears to significantly overshoot as compared with the nonpregnant patient. Regarding the lack of an accepted definition of hypotension per se, incidences of hypotensive events during cesarean section vary remarkably, measurements of blood flow demonstrated a 220% depending on which definition is applied. A meta- flow increase in the vena azygos in supine position, analysis of 63 studies reported a decrease of 80% mitigating the reduction in stroke volume and baseline alone or combined with systolic pressures explaining why a majority of more than 90% below 100 mmHg as most frequently used defini- remains unaffected of supine hypotensive syn- tions. However, among 15 differing definitions, the drome [2&]. Symptomatic women, in contrast, were spectrum of maternal hypotensive events ranged found to have significantly reduced flow rates in the between 7.4 and 74.1% [6]. vena azygos compared with asymptomatic women Nausea and vomiting are common and indica- in MRI phase contrast images [À0.15 (95% CI À0.30 tive symptoms of maternal hypotension. Several to À0.01) l/min], but with a comparable increase in hypotheses to its pathophysiology have been out- heart rate and a lack of any further compensatory lined, including the occurrence of gastrointestinal mechanisms [3&]. ischemia because of a reduced splanchnic perfusion More importantly – but lesser known – is the triggering a release of pro-emetic substances, such fact that a physiologic reduction of systemic vascu- as serotonin [7], as well as cerebral hypoperfusion lar resistance and its consequences provide a far causing ischemia of the vomiting center in the brain more decisive determinant for the occurrence and stem [8]. treatment of spinal-induced hypotension. Untreated hypotension may ultimately result in Peripheral arterial vasodilation already occurs loss of consciousness and aspiration and is not only during early pregnancy because of increased levels a serious maternal risk factor but also a cause of fetal of prostaglandins, progesterone, and estrogen. The adverse events. circulating peptide hormone relaxin and – espe- Due to missing vascular autoregulation, mater- cially in uterine vessels – increased levels of nitric nal hypotension promotes decreases in uteroplacen- oxide, as a promoter of improved uterine perfusion, tal blood flow, resulting in fetal hypoxia, acidosis are strong vasodilatory mediators. Resulting relative and low Apgar scores, correlated with severity and arterial underfilling stimulates the renin–angioten- duration of hypotensive events. sin–aldosterone system, thus leading to renal Approaches to maintain maternal blood pres- sodium and water retention, promoting expansion sure during cesarean delivery are an issue of of plasma volume and total body water. unabated interest for more than 60 years [9]. Along Dilutional anemia stimulates a permanent with increasing popularity of neuraxial anesthesia increase in heart rate, while atrial stretch because techniques in obstetrics, a plethora of studies on of volume overload is not only associated with an different substances, approaches, and regimens has elevated stroke volume but also induces remodeling been published since. processes in the cardiac wall and a further release Key issues are not only the choice of the most of natriuretic peptides, which have additional vaso- appropriate substance but also timing (prophylaxis dilatory effects. versus treatment) and method of administration However, elevation of plasma volume and car- (bolus versus continuous administration). On that diac output are not sufficient to counterbalance the account, this review highlights current recommen- decrease in vascular resistance, which may reach up dations against the background of most recent evi- to 40%, as mean arterial pressures are constantly dence (Fig. 1). 292 www.co-anesthesiology.com Volume 33 Number 3 June 2020 Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved. Hypotension after spinal anesthesia for c-section Massoth et al. FIGURE 1. Flowchart: gradual management of hypotension during cesarean section, starting with preventive measures prior to induction of spinal anesthesia. Precede to next step of algorithm if hypotension persists. Consider suggested vasopressor regimens as equally appropriate with regard to aforementioned conditions. IVCS, inferior vena cava syndrome; sbp, systolic blood pressure. SPINAL ANESTHESIA supplementation